Evaluation of genetic diversity and population structure of the Chinese chestnut (Castanea mollissima) by using NR-SSR markers

Abstract

China is the world's top producer of chestnuts. Population research through genetic techniques enhances our understanding of genetic diversity and population structure. Simple sequence repeats (SSRs) are the most extensively used markers in population genetics. In the present study, we evaluated the genetic diversity and genetic structure of natural Castanea mollissima populations with specific objectives including evaluating the geographic pattern of genetic diversity of wild Chinese chestnut; identifying spatial population structure and genetic differentiation between geographic locations; and proposing certain Chinese chestnut wild populations as reservoirs of genetic diversity for conservation. SSRs markers provide relevant and precise information on the dissemination of genetic diversity among populations having different categories of evolutionary drivers. Herein, the paper examines the genetic diversity and population structure of Chinese chestnut (C. mollissima) using nuclear SSRs. We analyzed 252 samples of C. mollissima from 14 populations and 11 different locations via eight multiplex SSR markers. Maps of genetic diversity parameters (e.g., number of alleles or N_A, expected heterozygosity or H_E, and private alleles richness or PAr) are generated through geo-statistical Inverse Distance Weighted (IDW) to construct a synthetic map that, in turn, reveals the population from Qinling-Daba Mountains possessed the highest genetic diversity (N_A = 8.3, H_E = 0.73). The analysis of molecular variance (AMOVA) analysis revealed that 89% of the genetic deviation found in C. mollissima exists within individuals and populations as opposed to 11% among different populations. Analysis of the SSRs using STRUCTURE identified five clusters with mixed population genetic structure by geographical location. Our results provide significant insight into the population structure of C. mollissima in China and present geographical locations of different gene pools to support conservation by identifying reservoirs of genetic diversity. These findings provide useful information related to markers, genetic diversity, and population structure of Chinese chestnuts.